Three dodecanuclear Mn clusters [Mn12O10(OMe)(3)(OH)(O2CC6H3F2)(16)(MeOH)(2)]center dot 8MeOH (1), [Mn12O10(OMe)(4)(O-2-CBut)(16)(MeOH)(2)] (2), and [Mn12O12(O2CBut)(16)(MeOH)4] (3) synthesized by reductive aggregation reactions are reported. Clusters 1 and 2 possess a central alkoxide-bridged planar Mn4 topology, whereas 3 is a new high-symmetry member of the normal Mn-12 family. Complexes 1 and 2 crystallize in the monoclinic space groups C2/c and P2(1)/n, respectively. Both consist of four Mn-IV and eight Mn-III ions held together by 10 mu 3-0(2-) ions, and either (i) one mu-OH- and three mu-MeO- groups for 1 or (ii) four mu-MeO- groups for 2. Complex 3 crystallizes in the orthorhombic space group Aba2 and possesses the normal Mn12 Structure but with terminal MeOH molecules. The cyclic voltammogram (CV) of 1 exhibits no reversible redox processes. Variable-temperature, solid-state dc and ac magnetic susceptibility measurements on 1 and 2 reveal that they possess S = 5 and 9 ground states, respectively. In addition, ac susceptibility measurements on complex 1 in a zero dc field in the temperature range 1.8-10 K and in a 3.5 G ac field oscillating at frequencies in the 5-1488 Hz range display a nonzero frequency-dependent out-of-phase (chi(M)") signal at temperatures below 3 K, with the peak maxima lying at temperatures below 1.8 K. For complex 2, two frequency dependent chi(M)" signals are seen, one in the higher temperature range of 3-5 K and a second at lower temperatures with its peak maxima at temperatures below 1.8 K. Single-crystal magnetization vs; dc field scans down to 0.04 K for 1 center dot 8MeOH and 2 show hysteresis behavior at <1 K, confirming that both complexes are new examples of SMMs.